Caries continues to be a major health problem in the United States and worldwide. Although recent evidence has shown a decline in the incidence of caries in children between the ages of 5 to 17, it should be noted that (a) children at the age of 17 still average 11 DMFS per child, and (b) caries incidence in people over 35 is increasing, particularly in the form of root surface caries. It is important to point out that recent evidence indicates that Streptococcus mutans play an important role in the initiation and/or progression of smooth surface lesions on root cementum. A hallmark characteristic of S. mutans is its ability to tenaciously adhere to and accumulate onto smooth surfaces in the presence of sucrose. It is our contention that the cell-surface glucan-binding lectin (GBL) of the mutans streptococci is a major virulence determinant, giving these organisms the ability to adhere to glucan-coated surfaces. To test this hypothesis , we propose to determine the role of the GBL as an adhesion and in cell-cell interactions which lead to accumulation of the bacteria on smooth surfaces. Moreover, we propose to study the physiology of GBL expression as it relates to various environmental conditions the organism would encounter in the oral cavity by conducting studies with a continuous- culture system. The specific aims of this research are (1) To purify the GBL, (2) To prepare polyclonal and monoclonal antibodies and to subsequently develop a whole-cell ELISA for detecting cell-surface GBL, (3) To determine the role of the GBL in (a) adhesion of S. mutans to glucan- coated hydroxyapatite, (b) cell-cell interactions of sucrose-cultured bacteria, and (c) colonization of smooth surfaces in the presence of sucrose, and (4) To study the expression of GBL on the surface of S. mutans in a continuous culture system. It is believed that such an approach will increase our understanding of how the mutans streptococci adhere to and accumulate on surfaces of teeth.